Is it unusual for a home to be rewired without a permit obtained?

Would it affect the value of the home? We are looking at a home that looks remodeled, with new electrical and wall heaters throughout entire home. City has no records of permits obtained for this. Is this a deal breaker not to buy a home?

It sure could be for me. I imagine it would depend greatly on the quality of work. If the visible work was done correctly...then "most likely" the stuff behind the walls is ok. It also depends on if they just replaced things vs adding new. Some places only allow replacement (switches, outlets, fixtures) w/o a permit. Any actual wiring changes or additions may require a permit and sometimes can only be done by licensed electricians. It really depends on what your area says. The Pro's will weigh in.

I would be leery since you have no idea of the quality or lack thereof that you cannot see and would be accepting. I have been on jobs without permits where the inspector made the contractor remove the drywall so it could be inspected.

Why this was done I can only guess, but most answers are not favorable.

Are the current homeowners available to you? If so, I'd certainly be talking to them about this.

I usually just ask my realtor that asks their realtor that asks them, its a mess. I should just directly contact them, but some people suggest not to do that. I don't understand legal reasons? I'm a first time home-buyer btw and a complete noob, but learning.

Many places require a certificate of occupancy. If work was not done with a permit that certificate could be revoked.

You could also end up in a twilight zone of catch 22s. As example where I live a couple was building a mother-in-law apartment behind their house. The city found out no permits were issued so they shut down construction. They could not get a permit to finish because the would be adding to a structure that was built without permit. They could not get a permit to tear down the partially constructed apartment and start from scratch because there was no record of permit for the original construction.

I'd say it really depends on the quality of the work, and how your city will handle it. If they aren't going to block the sale or anything silly like that, and the work looks to be of good quality it's probably fine. If the work looks suspect, then walk away from the deal. There are a lot of reasons that people don't get permits, some of them rather reasonable. Virtually every house that's 10 years old or more has some type of unpermitted work in it, so it's not like that is unusual.

It would be a good idea to hire an electrician for an hour to do an inspection of the house in addition to the usual home inspector that buyers hire. The HIs are generalists and not necessarily qualified to do a thorough inspection of the wiring.

There are a handful of shows on TV these days regarding incorrectly installed equipment with no permits pulled. I'd ask the question (or have the realtor ask the question), doesn't hurt to ask. If they get defensive, you know there's likely something hidden.

That said... are they just new devices? Maybe they were just replaced for that new feeling with no wiring altered. (maybe?)
As others have said, I would rely on some advice of your home inspector (hopefully a good one). I'd also be wary of significant renovations such as new living spaces. Ray hit it on the head that you don't want to end up with a part of the house which is illegal. For example, when I finished the basement here, it had to be reviewed by the zoning board to ensure it wasn't an apartment (not allowed in this area). Without permits/inspections/approvals, who knows what may happen down the road.

Just add a contingency to the purchase agreement that requires code compliance and proof of permit for the stuff you noticed as well as any other work done that is hidden or that you have not noticed. That gives you recourse and the ability to back out if they don't do it.

It's a buyer's market in most places, but if you really like the place otherwise, you could agree that the licensed electrical contractor of your choice (or mutually agreed) shall inspect the entire property ... All costs to repair non-compliant work shall be borne by the seller and work completed before an agreed upon date ... and so on.

I live in a code compliance area, which by ordinance requires the seller to get a certificate of code compliance before the sale. The municipal inspector will review the file and check the property for any undeclared improvements and non-compliant conditions, such as broken sash cords, missing receptacle and j-box plates, and will not issue the certificate until permits have been paid for and a re-inspection completed.

I would recommend being represented by a seasoned real estate attorney in this transaction. You'll have to pay for this of course but it should give you peace of mind that somebody is looking out for your interests. Money well spent.